The present invention relates to a pressure regulation apparatus ideally suited for controlling transportation of materials in either of at least two directions, and more particularly to a bi-directional (pressure-vacuum) single tube pneumatic system.
Pneumatic tube systems are well known for transporting capsules or carriers to one of several locations and back by selectively using pressure or vacuum to propel the carrier through a tube. Thereby, transactions requiring paper documentation may be conducted across barriers erected for security or across distances between parties.
Single tube installations are generally preferred as being simpler to install and use. Carriers are selectively transported in either direction within the single tube. To this end, blower assemblies are incorporated into a main station of the pneumatic tube system for selectively generating the pressure or vacuum. Much development has been performed in making blower assemblies that rapidly transfer the carrier yet slow the carrier at each station.
A challenge for known blower assemblies is to rapidly switch between pressure and vacuum modes in an economical and reliable manner. One technique is to provide two separately assigned blowers, either at opposite ends of the pneumatic tube system or within a blower assembly. Each blower is configured to propel a carrier in a direction opposite to the other. One blower assembly is unused during each operation, either from main station to remote station or remote to main station. Thus, such known separately assigned blower assemblies suffer from an undesirable requirement for having two large blowers with half of the pneumatic power unused.
In an attempt to overcome the advantages of separately assigned blowers, it is also known to have an electrically actuated air valve to selectively couple the intake or the exhaust of a single blower to the pneumatic tube system. Thereby, the full pneumatic power available is used during each operation. However, in addressing the excess pneumatic power disadvantage, such actuated blower assemblies introduce problems associated with the electrically actuated air valve. Specifically, the electrically actuated air valve reduces the overall reliability of the blower assembly by adding an component that can fail or that requires additional periodic servicing.
In addition, although reducing the per unit cost of the blower assembly by eliminating a second blower, the economic cost of using the pneumatic tube system is increased by the electrically actuated air valve. This increased economic cost is due to the delay in switching by the electrically actuated air valve as compared to separately assigned blower assemblies. The additional time in seconds for each customer transaction means that the pneumatic tube assembly can perform fewer customer transactions over a period of time. Thus, additional pneumatic tube assemblies have to be installed for additional capacity or customer-waiting time has to be increased.
Thus, a significant need exists for a blower assembly for a pneumatic tube system that rapidly switches between pressure and vacuum modes, yet does not leave half of the blower capacity unused during each operation.
The invention overcomes the above-noted and other deficiencies of the prior art by providing an apparatus and method for providing selectively switched pressure and vacuum to a pneumatic tube system that uses at least two pneumatic sources to cooperatively provide the required amount of pressure or vacuum during each operation. In particular, passive air valves, such as air spools, are positioned by sequencing the order in which the two pneumatic sources are activated to switch between pressure and vacuum. The passively switched air valves tend to be low cost, reliable, and rapidly positioned.
As an additional benefit, commercially available blowers tend to have a purchase price that is disproportionate to their pneumatic power capacity. In particular, it tends to be more economical to generate the same amount of pneumatic power with two smaller blowers than with one larger blower. Consequently, the approach of sequencing two smaller blowers that cooperate in achieving the desired pneumatic power capacity has an additional advantage over separately assigned blower assemblies.
In one aspect of the invention, a method is described for selectively providing pneumatic pressure and vacuum to a system manifold with an air shifter that communicates between an atmosphere port and the system manifold. For a selected one of pneumatic pressure and vacuum, the air shifter is pneumatically positioned by activating a first pneumatic source first. After a delay for the pneumatically positioning of the air shifter, a second pneumatic source is started to increase the selected one of pneumatic pressure and vacuum to the system manifold. Thereby, a reliable and rapid switching of the mode of the blower assembly is accomplished by pneumatically positioned elements.
In another aspect of the invention, a blower assembly is described for a pneumatic tube system that uses pneumatic pressure and vacuum to propel a carrier through a pneumatic carrier tube. The blower assembly shifts pressure or vacuum between a system manifold, which communicates with the pneumatic tube system, and an atmosphere port. The blower assembly accomplishes this shifting by including an intake passage and an exhaust passage that both communicate between the system manifold and the atmosphere port. The blower assembly includes two pneumatic sources that intake air from the intake passage and expel air into the exhaust passage. An intake closure device in the intake passage and an exhaust closure device in the exhaust passage are positioned to pressure mode when the one of the pneumatic sources is activated first and are positioned to vacuum mode when the other pneumatic source is activated first.
In yet a further aspect of the invention, a pneumatic tube system employs a blower assembly that includes an air shifter that pneumatically responds to a first blower being started before a second blower to provide pressure to a pneumatic carrier tube. The blower assembly further responds to the second blower being started before the first blower to provide vacuum to the pneumatic carrier tube. Thereby, all of the blower capacity is used for both providing pressure or vacuum to the pneumatic carrier tube, avoiding the uneconomical cost of dedicating one or more blowers to each mode of operation.
These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.